Constituents of Human Milk

Abstract

Breastmilk contains all the nutrients required by the newborn baby. It also contains non-nutritional components that may promote infant health, growth, and development, such as antimicrobial factors, digestive enzymes, hormones, trophic factors, and growth modulators. In some situations, breastmilk may also contain harmful components, such as pollutants, drugs, allergens, and viruses. Human milk has a unique composition, which differs from that of other mammals in its ingredients and their concentrations. Breastmilk composition is not constant and varies with stage of lactation, breastfeeding pattern, season, and parity. It also differs among individuals and among communities, for reasons that are not well understood. Maternal nutrition is an obvious candidate, but the situation is complex. Supplementation studies and cross-cultural comparisons have demonstrated that the total concentrations of fat, protein, and lactose are relatively insensitive to current dietary intake and nutritional status, whereas the fatty acid profile and the concentrations of several micronutrients, particularly water-soluble vitamins, are responsive to maternal diet. For many infants, nutrient intake from breastmilk becomes insufficient after four to six months, and other foods should be added to the diet. Nevertheless, breastmilk can continue to be a valuable nutrient source and to provide non-nutritional factors even for older children. Consequently, breastfeeding for one to two years as part of a mixed diet has many advantages, particularly for children living in impoverished circumstances.